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Philip
science forum beginner

Joined: 02 Jun 2005
Posts: 26

Posted: Thu Jun 29, 2006 2:04 am    Post subject: Peaks in electropherogram

hi
Any idea what kind of mathematical curves best describe the peaks in
electropherogram produced from capillary electorphoresis? A simple
Gaussian seems to provide a reasonable fit although i wonder if those
used in chromatography/spectroscopy will be better.

thanks
-p
Dr. Dickie
science forum beginner

Joined: 14 Jul 2005
Posts: 23

Posted: Thu Jun 29, 2006 11:05 am    Post subject: Re: Peaks in electropherogram

"Philip" <pcywong@stanford.edu> wrote in message
news:e7vcgc\$1b8\$1@news.Stanford.EDU...
 Quote: hi Any idea what kind of mathematical curves best describe the peaks in electropherogram produced from capillary electorphoresis? A simple Gaussian seems to provide a reasonable fit although i wonder if those used in chromatography/spectroscopy will be better. thanks -p

Theoretically, the peak should be Gaussian (IIRC- electrophoresis peaks are
treated the same as other chromatography peaks). In reality, most peaks are
not; however, unless you have a problem with the compound of interest, most
peaks do not deviate from Gaussian (1-4 moments) enough to cause significant
problems in area calculation.
Sure, everybody and his brother can cite an example where a peak deviated,
but still MOST do not deviate enough to cause significant problems and
usually the software with the instrument can overcome small deviations..
What methods does the software that came with the instrument use?

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David Stone
science forum beginner

Joined: 27 Mar 2006
Posts: 14

Posted: Thu Jun 29, 2006 11:30 am    Post subject: Re: Peaks in electropherogram

In article <e80bsj\$j74\$1@nntp.aioe.org>,
"Dr. Dickie" <Dr_Dickie@hotmail.com> wrote:

 Quote: "Philip" wrote in message news:e7vcgc\$1b8\$1@news.Stanford.EDU... hi Any idea what kind of mathematical curves best describe the peaks in electropherogram produced from capillary electorphoresis? A simple Gaussian seems to provide a reasonable fit although i wonder if those used in chromatography/spectroscopy will be better. thanks -p Theoretically, the peak should be Gaussian (IIRC- electrophoresis peaks are treated the same as other chromatography peaks). In reality, most peaks are not;

Theoretically, it should be an exponentially-modified gaussian, since
the profile is still broadening as it is being detected. Not much
practical gain to be had from that unless you are dealing with very
low plate numbers, though. (Which, by definition, you almost certainly
are not in CE!)

 Quote: however, unless you have a problem with the compound of interest, most peaks do not deviate from Gaussian (1-4 moments) enough to cause significant problems in area calculation.

Agreed, although it does depend a little on exactly what you want to
do with the data once you've fitted the function - can the original
poster elucidate a little?
Philip
science forum beginner

Joined: 02 Jun 2005
Posts: 26

Posted: Thu Jun 29, 2006 7:42 pm    Post subject: Re: Peaks in electropherogram

Dr. Dickie wrote:

 Quote: Theoretically, the peak should be Gaussian (IIRC- electrophoresis peaks are treated the same as other chromatography peaks). In reality, most peaks are not; however, unless you have a problem with the compound of interest, most peaks do not deviate from Gaussian (1-4 moments) enough to cause significant problems in area calculation. Sure, everybody and his brother can cite an example where a peak deviated, but still MOST do not deviate enough to cause significant problems and usually the software with the instrument can overcome small deviations.. What methods does the software that came with the instrument use?

I only have the raw data and intend to fit the curves on my own...
Philip
science forum beginner

Joined: 02 Jun 2005
Posts: 26

Posted: Thu Jun 29, 2006 7:49 pm    Post subject: Re: Peaks in electropherogram

David Stone wrote:

 Quote: Theoretically, it should be an exponentially-modified gaussian, since the profile is still broadening as it is being detected. Not much practical gain to be had from that unless you are dealing with very low plate numbers, though. (Which, by definition, you almost certainly are not in CE!)

yep, i did try to fit an exponentially-modified gaussian and the fit
statistics is slightly worse that a simple gaussian.

 Quote: Agreed, although it does depend a little on exactly what you want to do with the data once you've fitted the function - can the original poster elucidate a little?

There are two objectives. One is to determine the area and the other is
to reconstruct over-saturated peaks. The over-saturated peaks are
cut-off but i think i have sufficient data to at least get an estimated
fit.

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